Abstract [11 C] FLB 457 is a high affinity dopamine D 2 receptor radioligand that is used for visualisation and quantitation of extrastriatal dopamine D 2 receptors with positron emission tomography (PET). In this study, we report a comparison regarding the specific radioactivity of [11 C] FLB 457 obtained by two different methods of synthesising [11 C] methyl iodide. In addition, the synthesis of unlabelled FLB 457 and the corresponding desmethyl-precursor, ...